The present invention relates generally to wellsite operations and, in an embodiment described herein, more particularly provides a well completion tool having pressure relief capabilities, and associated methods.
In many wellsite operations, fluid is delivered into a well and then returned. For example, in drilling operations, drilling mud is typically circulated into a well through a drill string and returned to the earth's surface through an annulus formed between the drill string and the wellbore. In stimulation operations, fluid may be delivered to the wellbore through a fluid delivery flowpath of a well tool and returned along a fluid return flowpath.
Where the stimulation operation is, for example, a formation fracturing operation, proppant may be suspended in the fluid when it is delivered to the wellbore by pumps at the earth's surface. To prevent return of the proppant with the fluid through the fluid return flowpath, one or more screens are generally attached to the well tool, so that the returned fluid does not include the proppant. Unfortunately, where very high flow rates are used, the wellbore surrounding the well tool may fill quickly, with proppant, covering the screens, substantially restricting fluid flow therethrough and creating excessive differential pressure across portions of the well tool. This situation may occur so rapidly that there is not enough time to shut down the pumps and prevent collapse of the screens and/or other portions of the well tool. The problem also exists in other well completion operations, such as gravel packing.
In the past, attempts to remedy this problem have focused on preventing excessive pressure differentials from being applied to the well tool at the earth's surface. For example, sensors may be utilized at the earth's surface to monitor the pressure applied to the fluid delivered into the well and the pressure of the fluid returned from the well. If the differences between the pressures become excessive, the pumps may be slowed or stopped as needed to decrease the pressure differential.
In very high flow rate operations, however, the distance between the well tool and the sensors, and the resulting stored energy in the large mass of fluid flowing through the delivery and return flowpaths, produces a significant lag between the time at which remedial measures are taken at the earth's surface and the time at which a decrease in the pressure differential is experienced at the well tool.
From the foregoing, it can be seen that it would be quite desirable to provide pressure relief capabilities in well tools utilized in wellsite operations. In particular, these pressure relief capabilities could be incorporated into the well tool, in order to minimize any time lag between the occurrence of excessive differential pressure and relief of that differential pressure. Additionally, where the fluid may carry, particulate matter, such as proppant or gravel, a pressure relief device incorporated in the tool could include a filtering device. It is accordingly an object of the present invention to provide such a well tool and associated methods.